GitHub nuked my clearly non-infringing patch to youtube-dl and the non-infringing GitHub issue. So here's a mirror:

• my patch: [youtube] Fix download of auto-captions when subtitles are available
• PR #24823 was recovered by the gharchive restoration effort: 24823.json

To apply it you will need a copy of youtube-dl. You can find latest release (incl. source code) on yt-dl.org, its official website. In addition, the development versions and source code history is available:

• https://gitee.com/mirrors/youtube-downloader.git on Gitee appears to be a very up-to-date clone, including the 2020-10-22 commit referenced in Google Web Cache^{archive.is, archive.org}, and the earlier 2020-10-17 commit referenced in an Internet Archive crawl.
• Internet Archive has a ZIP snapshot from https://codeload.github.com/ytdl-org/youtube-dl/zip/master. Its contents correspond to the 2020-10-17 commit 4eda10499.
• You can also get a snapshot from the Debian git. Or a source package from your local mirror. The Debian git is different (e.g. it includes files specific to Debian packaging and excludes the .github directory), however, all source code files at the Debian git HEAD seem to match the upstream code at the tag 2020.09.14.
• Finally, keen eyes might observe that yt-dl.org tarballs redirect to the maintainer's temporary GitLab repo, which includes signed tags. People on Freenode's #youtube-dl frequently mention https://git.osuv.de/star/youtube-dl as a reliable mirror.

The releases and git tags are signed^archive.org and you can find the two relevant keys on your favorite PGP key server.

For more context, see "Music industry forces widely used journalist tool offline" from the Freedom of the Press Foundation and The Github youtube-dl Takedown Isn't Just a Problem of American Law from the Electronic Frontier Foundation.